This invention relates generally to the field of power supplies, and, in particular, to standby mode power supplies for television receivers.
The power consumed by electronic equipment in the standby mode is becoming an increasingly visible public policy issue. For example, an article in the Sep. 19, 1997, issue of Europe Energy reports that the European Commission regards reducing the energy consumed by electronic equipment in the standby mode of operation as a priority. The article further states that the Commission has concentrated its initial efforts at reducing the standby power consumption of televisions and VCRs, and that it has elicited voluntary commitments from manufacturers of such products to progressively reduce average standby power consumption.
Modern televisions can have a standby power consumption of about 5 to 10 Watts caused by the degaussing circuit and switched mode power supply running in standby mode. Televisions that have an additional standby power supply and disconnect the degaussing circuit can reduce the power consumption to 1 Watt.
In a conventional power supply arrangement for a video display apparatus, a primary winding of a standby transformer is coupled to the AC mains. A transformed voltage across a secondary winding of the standby transformer is full-wave rectified and is regulated by some form of linear regulation to provide power for the video display apparatus in a standby mode of operation. This standby power supply consumes power as long as the video display apparatus is connected to the AC mains, and thus also consumes power during the run mode of operation. During standby mode, power losses are incurred partly due to switching losses. U.S. Pat. No. 6,043,994 proposes a power supply for reducing standby power consumption attributable to a start-up resistor of the switched mode power supply controller integrated circuit IC.
It is therefore desirable to provide a simple and cost-effective method for reducing the standby power consumption attributable to the switching losses.